Scientists wage war on fire ants

Imported fire ants are a fact of life for Mississippians and most of their neighbors across the Southeast. Scientists believe imported fire ants first arrived in the United States during 1918 at the port of Mobile, Ala., as stowaways on a ship from South America. Since then, the invaders have spread across most of the Southeast. Their name comes from the “fiery” sting of their bite.

Mississippi State University entomologist and Mississippi Entomological Museum director Richard Brown said there are two species of imported fire ants in Mississippi: Solenopsis invicta (red fire ants) and Solenopsis richteri (black fire ants). There's also a hybrid cross of the two imported species.

“All three are serious pests because their mounds can interfere with crop cultivation, make pasture and lawn maintenance difficult, kill young birds and small animals, and inflict painful, possibly deadly bites on humans,” Brown said. “The ants reproduce rapidly and a mound can reach a height of 10 inches or more with populations often topping 100,000.”

A variety of control measures have been used against fire ants, ranging from pouring boiling water into mounds to a host of insecticide treatments. Success rates vary, but nothing has stopped the pests' spread.

In 2003, Brown and other scientists with the Mississippi Agricultural and Forestry Experiment Station at MSU began a project that may provide new approaches to the fire ant problem. The entomologists, plant pathologists and agricultural engineers, along with graduate students under their direction, are conducting research related to their respective areas of expertise. The goal is to fill in the gaps in scientific knowledge of fire ants and their impact.

Entomologist Jack Reed is looking at ways to control fire ants in row crops and other locations without reducing native ant populations. He is working with agricultural engineers Filip To and David Smith on equipment to detect and apply control treatments just to fire ant mounds in row crops. The result will be more effective and economical control of the pest in crops.

Another part of Reed's fire ant research is being conducted with U.S. Department of Agriculture-Agricultural Research Service entomologist J.T. Vogt in Stoneville, Miss., and involves determining when fire ants are the most active.

“We're looking for times when fire ants are most active so treatments can be made when they will have a high potential for killing those species without affecting native ants,” Reed said. One reason fire ants have been so prolific since arriving in the South is the absence of natural enemies. Plant pathologist Richard Baird and graduate student Sandra Woolfolk are digging into mounds in hopes of finding pathogens that can be used for biological control.

“We are assuming that since the population of ants in the mounds is so high, there might be fungi or bacteria present that might be pathogens that can be used for fire ant control,” Baird said. “In tests at MSU's Insect Rearing Laboratory, several of the pathogens we've found were effective in repelling fire ants.”

During the spring and summer of 2004, Woolfolk will conduct additional fieldwork with the red imported fire ant, which is expected to become the dominant variety in Mississippi.

Entomologists Peter Ma and Gerald Baker are studying the physiology and morphology of fire ants as part of their search for more effective control methods.

“We are studying the ants' physiology in order to develop a way to disrupt their communication,” Ma said. “This could be used to block their mating cycle.”

Ma and Baker also are studying the interaction between fire ants and a type of small wasp-like insect that preys on the ants, with the hope of using information about the communication between the prey and the predator in control methods.

Entomologist Evan Nebeker and graduate students under his direction are studying the ants in forest environments.

While fire ants are most common in pastures and other open areas, they do inhabit forests, especially in areas adjacent to open fields, Nebeker said.

“We know fire ants destroy quail nests and cause other problems for wildlife, but we don't know their full impact on wooded areas,” he said.

Graduate students Tim Mensel and Sara Self are studying how various forestry practices influence movement and distribution of fire ants and how the ants impact commercial Christmas tree operations.

Nebeker and his students also are locating areas along the Natchez Trace that attract large numbers of fire ants.

“Identifying high-risk areas will help identify the characteristics that attract fire ants,” Nebeker said. “It also will allow control measures to be concentrated on areas where the ants are a threat to visitors.”

While imported fire ants cause problems for Mississippians throughout the state, there are dozens of other varieties of ants that go virtually unnoticed. Identifying, studying and recording data is part of the research conducted by Brown and Joe MacGown, assistant curator of the entomological museum.

“Ants are among the most numerous creatures on the planet, but they are a very troublesome group to identify and classify,” Brown said. “As part of an effort to better understand the ants of Mississippi, the museum is conducting ongoing surveys for ants in the state. The ultimate goal is an updated species list with distribution maps, identification keys and diagnostic drawings.”

The multidisciplinary study of fire ants is expected to result in a much clearer understanding of the pest, but the scientists agree that their work likely won't result in a “magic bullet” for control. They do, however, expect the results of their work to provide guidelines for more effective and economical ways to reduce problems with fire ants in crops, lawns and other areas where they cause the most damage.

Bob Ratliff is a science writer for University Relations at Mississippi State University.